1. The Enigma of the Respiratory Chain Supercomplex
Dusanka Milenkovic, James N. Blaza, Nils-Göran Larsson, Judy Hirst 
Cell Metabolism 
Volume 25, Issue 4, Pages (April 2017)
DOI: /j.cmet
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2. Figure 1 Structures of the Respirasome
(A) The arrangement of CI (orange), the CIII dimer (the monomers are shown in blue and cyan), and CIV (magenta) in the porcine respirasome, viewed along the membrane plane.
(B) The porcine respirasome viewed from the matrix.
(C) Comparison of the porcine and ovine respirasome structures. The structures were superimposed using the structure of the CIII dimer, to reveal the different relative positions of CI and CIV. CIV is shown as transparent over-lapping shapes (pink, porcine respirasome; magenta, tight ovine respirasome; blue, loose ovine respirasome). The transmembrane helix in CIV COX7A is highlighted to show how it moves relative to CIII UQCR11, which has been modeled in two slightly different positions. The figure was created using 5GPN.pdb (Gu et al., 2016) (provided by the authors before release by the protein data bank), 5J4Z.pdb and 5J7Y.pdb (Letts et al., 2016).
Cell Metabolism  , DOI: ( /j.cmet )
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3. Figure 2
The Presence of Supercomplexes and Respirasomes Depends on COX7A2L and Cardiolipin
(A) The respiratory chain complexes of mouse strains harboring the long COX7A2L isoform (e.g., CD1 and BALB/c) are organized in respirasomes (I/III2/IV) and supercomplexes (I/III2 and III2/IV).
(B) Strains carrying the short COX7A2L isoform (e.g., C57BL/6 and DBA/2J) lack the III2/IV supercomplex.
(C) Deficiency of the mitochondrial signature phospholipid, cardiolipin, leads to destabilized supercomplex assemblies (light colors).
Cell Metabolism  , DOI: ( /j.cmet )
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4. Figure 3
Proposal for How Respirasomes Form in the Presence and Absence of the Long Isoform of COX7A2L
(A) Respirasome formation in the presence of the long isoform of COX7A2L. Top: the individual, fully assembled complexes are CI, the CIII dimer, and the CIV monomer. COX7A2L is weakly associated with CIII (it is not observed in the structure of CIII) and is proposed to interact with subunit UQCR11. COX7A is also shown as a CIV subunit. Middle: a tight interface forms between CIII and CIV when COX7A2L replaces COX7A. Bottom: the III2/IV supercomplex associates with CI to form the respirasome. It is also possible that CIII and CIV both associate with CI before the III2/IV interface forms.
(B) Respirasome formation in the absence of the long isoform of COX7A2L. Top: The individual, fully assembled complexes are CI, the CIII dimer, and the CIV monomer. COX7A is shown as a CIV subunit. Bottom: CIII and CIV both associate with CI but a tight interface is not formed between them. The III2/IV supercomplex is unstable.
Cell Metabolism  , DOI: ( /j.cmet )
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5. Figure 4 Ubiquinone and cyt c Binding Sites in the Respirasome
(A) The transmembrane helices in the respirasome, shown in the same orientation as Figure 1B. The exit from the CI ubiquinone-binding site is indicated, along with the positions of the two ubiquinol-binding sites in CIII.
(B) The respirasome viewed from the intermembrane space with two cyt c molecules shown to approximately indicate their binding sites on CIII, and the negatively charged patch on CIV where the reduced cyt c is reoxidized. The figure was created using 5GPN.pdb for the porcine respirasome (Gu et al., 2016) (provided by the authors before release by the protein data bank).
Cell Metabolism  , DOI: ( /j.cmet )
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6. Figure 5
Functional Data that Demonstrate There Is Only One Q Pool in the Inner Mitochondrial Membrane
(A) Rates of O2 reduction by submitochondrial particles (SMPs) measured using NADH, succinate, or both substrates together. The sum of the individually measured rates is also shown. For SMPs prepared with additional cyt c, the rate of CIII+CIV catalysis is high so adding both substrates together increases the overall rate. For SMPs prepared without additional cyt c, the rate of CIII+CIV catalysis is low so the rate of O2 reduction is constant, regardless of which substrate(s) are added.
(B) Reduction of the cyt c1 heme in CIII and of cyt c upon addition of NADH, succinate, or both substrates together, followed spectroscopically. The relative extents of reduction are indicated for the ends of the traces shown and in all cases the hemes are close to fully reduced.
(C) The rates of different reactions measured in the same set of SMPs. Electrons can pass from CII to CI (in reverse electron transport) as fast as from CI to CIII+IV. Reverse electron transport from succinate to NAD+ requires ATP hydrolysis to overcome the potential difference. Data from Hirst and coworkers (Blaza et al., 2014).
Cell Metabolism  , DOI: ( /j.cmet )
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